The tunnel is actually a system of three separate tunnels, two of which branch out from one long-running tunnel from Harwood to Wichita Gardens, while the branch tunnels lead to Rockford and Francis International. The Francis International portal consists of two separate openings on either side of a surface road, each for one traffic direction.

Much of the tunnel runs underwater.

GTA III

In 2001 (the time setting of GTA III), the tunnel is initially inaccessible, citing that tunnel construction was still incomplete and had been delayed several times. At the time of the tunnel's delays, the tunnel's chief engineer and project director is Winston Cole, while the project's financier is FBC Financial Group. The tunnel was originally scheduled for completion in April 2001, but was delayed to late-October 2001, coinciding with GTA III's timeline. The projects has been plagued with problems, such as leakage, as well as corruption, leading to the project winding up over-budgeted and behind schedule.

During the game, the tunnel would be opened to the player in phases: first with the segment linking Portland and Staunton following "Last Requests", then the segment linking the Portland-Staunton exits to the Shoreside Vale exits following "A Drop in the Ocean".

If the player manages to reach Staunton before it is unlocked after "Last Requests", the tunnel is revealed to only be sealed from the Portland end, allowing the player to access Shoreside Vale via the tunnel (as the Shoreside Lift Bridge remains non-operational). After "Last Requests", the route to the Shoreside Vale exits is sealed off from traffic until "A Drop in the Ocean". If the player ventures towards into the Shoreside stretch, traffic between the two Shoreside Vale portals is revealed to be free flowing, lending to the idea in GTA Liberty City Stories that these ends of the tunnel have been opened to the public longer than the Staunton and Portland ends.

GTA Liberty City Stories

In 1998 (the time setting of GTA Liberty City Stories), the tunnel is revealed to be only partially completed, as only the Shoreside
Vale ends of the tunnel are operational, while the Shoreside Vale-Staunton stretch is still under construction; digging towards Portland had not even begun. At the time, the tunnel's future Portland exit is occupied by the Portland ferry terminal, which is temporarily shut down following city-wide protests against the construction of both Callahan Bridge and the tunnel, which will render the ferries obsolete. The ferry returns to service after compromises and assurance by a newly elected mayor to retain the ferry service, but was ultimately shut down, as its Portland terminal is soon cleared away for the Porter exit.

During the construction of the tunnel, workers accessed the abandoned subway line, which is published in a Liberty Tree article entitled "A Hole Too Far!". Toni Cipriani, on orders from Donald Love, uses the Porter Tunnel to access the old subway line and plants explosives. Toni uses the abandoned subway to escape and the explosives detonate, destroying Fort Staunton, setting back the Porter Tunnel development.